This invention is concerned with mobile agricultural machines and more particularly with adjustable disposition or spacing of one functional component with respect to another in such machines as, for example, in the control of reel height with respect to cutterbar in a gathering unit of a harvester. The harvester reel application will be used as an example in the following discussion.
Typically, linear actuators such as hydraulic cylinders, are used to make on-the-go adjustment of position of a functional or material handling component such as the harvester reel. Range of adjustment is limited by the hydraulic cylinder stroke but relative disposition of this range can be selectively adjusted or shifted if, for example, a series of spaced cylinder attaching points are provided for one or both ends of the cylinder, thus providing a coarse stepped adjustment of operating range. In many applications, variables such as crop and operating conditions, deflection of functional components, or manufacturing variations make it desirable to provide means for supplementary fine adjustment. For example, sometimes it is desirable to set a harvester reel to clear a cutterbar by no more than one inch, maintaining that clearance uniformly along the length of the cutterbar. Typically, the reel is supported by reel arms, one at each end of the reel, each end controlled by a single hydraulic cylinder. Supplementary or fine adjustment can provide a range of settings within or overlapping the coarse steps provided by spaced cylinder mounting holes and also the possibility for independent differential adjustment of each end of the reel to maintain it parallel to the cutterbar. It is known to provide such fine adjustment by interposing a pivot bracket with threaded screw adjustment at the attachment of the hydraulic cylinder to the reel arm. More generally, of course, it is also known to provide means for cylinder rod effective length adjustment as part of the attachment of a connecting member such as a clevis or eye-end to the rod of a hydraulic cylinder.
Again, using the harvester reel as an example, it is typical to provide another function associated with the reel lift means--a safety device to prevent inadvertent lowering of the reel. Typically, with the reel raised and hydraulic cylinders extended, a channel-shaped strut or stop arm is pivotably carried on the pin connecting the hydraulic cylinder rod to the reel arm and swung down into position over the cylinder rod when needed. The length of the stop or strut is such that after only a small retraction of the cylinder and lowering movement of the reel, the stop engages the hydraulic cylinder body to prevent further retraction and lowering of the reel.
Disadvantages of the known methods of providing fine or supplementary adjustment of reel height include, for the pivoting bracket type referred to above, clumsy appearance and the potential cost penalty of requiring stress-concentrating holes at a highly stressed portion of the reel arm; and, in the case of the conventional adjustable-length hydraulic cylinder rod, the need to disconnect the rod from the reel arm to permit adjustment.